The current development towards truly mobile computing and networking has brought on the evolvement of various access technologies that also provide the users with access to the Internet when they are outside their own home network. At present, wireless Internet access is typically based on either short-range wireless systems or mobile networks, or both.
Short-range wireless systems have a typical range of one hundred meters or less. They often combine with systems wired to the Internet to provide communication over long distances. The category of short-range wireless systems includes wireless personal area networks (PANs) and wireless local area networks (WLANs). They have the common feature of operating in unlicensed portions of the radio spectrum, usually either in the 2.4 GHz Industrial, Scientific, and Medical (ISM) band or in the 5 GHz unlicensed band.
Wireless personal area networks use low cost, low power wireless devices that have a typical range of about ten meters. The best-known example of wireless personal area network technology is Bluetooth, which uses the 2.4 GHz ISM band. It provides a peak air link speed of one Mbps, and power consumption low enough for use in personal, portable electronics such as PDAs and mobile phones. Wireless local area networks generally operate at higher peak speeds of 10 to 100 Mbps and have a longer range, which requires greater power consumption.
Wireless LAN systems are typically extensions of a wired network, providing mobile users with wireless access to the wired network. Examples of wireless local area network technology include the IEEE 802.11a, which is designed for the 5 GHz unlicensed band, and uses orthogonal frequency division multiplexing (OFDM) to deliver up to 54 Mbps data rates; the 802.11b, which is designed for the 2.4 GHz ISM band and uses direct sequence spread spectrum (DSSS) to deliver up to 11 Mbps data rates; and the HIPERLAN Standard, which is designed to operate in the 5 GHz unlicensed band.
In wireless LAN technology, two basic network topologies are available for network configuration: an ad-hoc network and an infrastructure network. An ad-hoc network is formed by two or more independent mobile terminals without the services of a base station, i.e. in an ad-hoc network the terminals communicate on a peer-to-peer basis. An ad-hoc network is normally formed for temporary purposes. The infrastructure network, in turn, comprises one or more wireless base stations, called access points, which form part of the wired infrastructure. In a typical network of this type, all traffic goes through the access points, regardless of whether the traffic is between two terminals or a terminal and the wired network, i.e. the mobile terminals do not communicate on a peer-to-peer basis. The mobile terminals are provided with wireless LAN cards, whereby they can access the wired network or set up an ad-hoc network. In an infrastructure network an access point and at least one terminal is said to form a Basic Serving Set (BSS), while an ad-hoc network is also termed an Independent BSS (IBSS).
When a wireless terminal tries to access an infrastructure network, the user of the terminal is authenticated before the terminal may become a member of the infrastructure network. After the authentication has been performed and the terminal has associated itself with the infrastructure network, the user may start to use the services available through the relevant access point.
When using the services available through the access points of various networks, such as corporate or home networks, the user may also wish to establish or join an ad-hoc network. For example, the user might wish to download content, such as music, from a near-by terminal or play a game with a user of another terminal while simultaneously being associated with an infrastructure network. A drawback related to the current networks is that if the user enters the ad-hoc operation mode, the existing association in the infrastructure network is removed. In other words, the user of the terminal has to be authenticated again and a new association has to be created when the user leaves the ad-hoc mode and re-enters the infrastructure network. This drawback relates to the fact that in a beacon-based system the terminals have to monitor the information broadcast in the beacon frames. In the infrastructure networks, each access point sends beacon frames at regular intervals, and the terminals synchronize their operation with the rhythm of the beacon transmissions. The beacon transmissions include, for example, timing information and information about the capabilities of the transmitting access point. At present, simultaneous operation in two different beacon-based networks is not possible, but an existing association in one network is lost if another network is entered.
The present invention seeks to accomplish a solution by means of which the above drawbacks of wireless beacon-based networks may be alleviated.